Systhesis Of Cobalt Oxide And Its Application As Anode Material For Li-Ion Batteries

Recently, more and more attention has been were paid on rechargeable Li-ion Batteries. In order to improve the specific capacity, intensive experiments had been made on anode material. Based on plenty of reports in literature, the loss of capacity is mainly caused by the aggregation and pulverization of the electrode particles that appears in the discharge/charge cycles. In this paper, we enhance the performance of batteries by preparing cobalt oxide materials with porous structure, carbon coating or recombination with graphene. The main details in my improved experiments are as following:(1) Novel porous CO3O4polyhedral architectures have been successfully prepared using CoCl2·6H2O and (NH4)2C2O4as the raw materials. The process combined a facile hydrothermal synthesis of uniform cobalt oxalate precursors with subsequent heat treatment in air. The samples were characterized respectively using XRD、SEM and TEM to identify its phase, morphologies and microstructures. The specific surface area was investigated using N2adsorption-desorption. Electrochemical properties of the products were evaluated using CR2025-type coin cells and the results reveals that:the porous polyhedral Co3O4presents an initial discharge capacity of1546mAh/g, and maintains a reversible capacity of432mAh/g after45discharge/charge cycles. The better electrochemical performance of porous Co3O4can be attributed to its special porous structure, which provides the structural flexibility for volume change and the routes for fast Li+diffusion.(2) Uniform CoO/C polyhedra were synthesized by impregnating hydrothermally fabricated Co3O4polyhedra with sugar solution followed by calcination in Ar atmosphere. When tested in the prepared batteries as anode material, the CoO/C polyhedra exhibited an initial discharge capacity of1025mAh/g, and remained a reversible capacity of510mAh/g after50cycles at a current density of100mA/g. High Coulombic efficiency over99%and improved rate capability were achieved for the CoO/C polyhedra. Hierarchical structure and high porosity was benefit to the infiltration of electrolyte and tolerant volume expansion, and may be responsible for the improved electrochemical property.(3) Firstly, we synthesized Co(OH)2/graphene in the condition of microwave using COCl2·6H2O, NaOH and prepared GO. Co3O4/graphene compound was successfully fabricated by the calcination of Co(OH)2/graphene in a tube furnace after2h. The phase of prepared material was indicted as cubic phase using XRD, the good disperse of Co3O4particles in the Co3O4/graphene hybrid was showed by the SEM and the TEM, meanwhile we observed its microstructure using the TEM. The content of graphene is about25%from the experiment of TG. We made the half lithium-ion battery from the prepared material and investigated the performance and the results show that it has excellent cycling properties and good rate performance.